Two major types of earplugs in widespread use are earplugs with bodies of elastomeric foam, and earplugs that are of nonfoam elastomeric material and that have flanges, or fins. Foam earplugs are formed of an elastomer with more than 25% of the volume being gas bubbles, and actually with more than 50% of the volume consisting of gas bubbles. Such foam earplugs are usually disposable in that they are commonly discarded by factory workers after each use.
One example of a nonfoam earplug with fins, shown in U.S. Pat. No. 6,241,041, has long and thin fins extending at rearward and radially-outward inclines from a stem portion or stem. Such finned earplugs generally do not block sound as well as foam earplugs, but the finned earplugs are reusable in that they stand wear and can be used many times. The noise blocking ability of an earplug is usually defined by its NRR number (noise reduction rating) according to a rating system established by the EPA (Environmental Protection Agency) of the United States. A finned nonfoam earplug of the type described in U.S. Pat. No. 6,241,041 has an NRR rating of 22 to 24. A foam earplug of the type described in U.S. Pat. No. 4,774,938 has an NRR rating of 34. It would be desirable if a finned nonfoam earplug had a higher NRR rating.